The triquetra has been found on runestones in Northern Europe and on early Germanic coins. It presumably had pagan religious meaning and it bears a resemblance to the Valknut, a symbol associated with Odin.
G Scale Trains are usually referred to as Garden Trains since they are the largest of the model trains and are used outdoors as well as indoors.
Most motors used in model trains today are brushed DC permanent magnet motors. These operate at maximum speeds around 10,000 rpm (some can operate at higher speeds) using gear trains to reduce the speed at which the wheels turn, and thus can be rather noisy.